Dear Maintainer, I've got the exact same error that was reported in 2012 here: https://bugs.php.net/bug.php?id=62398 The only diference is that in my case I've only reproduced in 'include' (not require). The apache error log show lines like these: Mar 17 15:14:22 web www.example.com: [Mon Mar 17 15:14:22 2014] [error] [client 127.0.0.1] PHP Warning: include(): Filename cannot be empty in /var/www/example.com/path/myfile.php on line 10, referer: http://www.example.com/xx/yyy Mar 17 15:14:22 web www.example.com: [Mon Mar 17 15:14:22 2014] [error] [client 127.0.0.1] PHP Warning: include(): Failed opening '' for inclusion (include_path='.:/usr/share/php:/usr/share/pear') in /var/www/example.com/path/myfile.php on line 10, referer: http://www.example.com/xx/yyy All apc settings are default unless: apc.stat=0 It works fine with squeeze.